When assembly or fitting is automated by employing a working robot, there are cases where the robot judges the success or failure of the work after completion of the work.
Conventional methods of checking the state of a work target can be classified into a method of checking after the completion of a work and a method of checking during a work. As the method of checking after the completion of a work, there is a method of checking a work target in a non-contacting manner by using a three dimensional visual sensor (for example, International Publication Pamphlet No. WO 98/17444).
In addition, there is a method in which, after the completion of assembling, a work target is gripped with a hand once again by performing an assembling action, and force sense information obtained during the process is compared with force sense information obtained at the time of success (for example, Japanese Laid-Open Patent Publication No. 08-174459).
As the method of checking during a work, there is a method of judging success or failure by detecting an impact sound at the time of fitting by making use of a microphone rather than the force sense information (for example, Japanese Laid-Open Patent Publication No. 09-123078).
However, according to the conventional methods, the judging of success or failure of a work may not be successfully achieved without being influenced by surroundings, a variation in individual works, and the placement of a latch, and nearly without disturbing the work.